1. Field of Invention
This invention relates to monitoring loads in fastenings, and more particularly to in-fastening load monitors.
2. Description of the Related Art
Fasteners are used in a wide variety of industrial installations where achieving proper fastener loading (tension) and maintaining this loading in service can be problematic. Monitoring the load on a fastener during installation and service can be equally problematic.
Many industrial fastening applications require a predetermined loading at installation and periodic monitoring of loading to ensure that loading remains within an acceptable range. Checking the loading with a torque wrench typically requires loosening and then retorquing of the fastening. This is particularly onerous in high corrosion and high cycle loading applications.
Overtightening a fastener can lead to catastrophic failures. Conversely, fasteners typically experience some loss of tension in service due to, for example, a variety of in-service occurrences including: relaxation (thread embedment), vibration loosening, compressive deformation in the joint or flange, temperature expansion or contraction, etc. Loss of tension from these occurrences can cause misalignment or premature wear in a bolted assembly, leakage (in applications where the fastener is used for sealing), or catastrophic joint failure due to excessively high loads on other members of the assembly.
In certain applications, knowledge of a fastener load, upon installation and over time, is desirable for avoiding the potentially dangerous consequences of a compromised or loosened fastener, such as slippage, wear, leakage and/or possible failure. In other applications, for example when working with a group of bolts around a flange of a sealed assembly, it is important to evenly tighten the group of bolts. By uniformly tightening a group of bolts or studs to an appropriate load, and maintaining this load over time, potential failures are less likely to be experienced
Accordingly, improvements are sought in determining and monitoring fastener loading.